1. Field of the Invention
The present invention relates to a liquid ejection head and a method of manufacturing a liquid ejection head, and more particularly, to technology for achieving high-density arrangement of electrical wires which supply drive signals to actuators that cause liquid to be ejected from ejection ports of a liquid ejection head.
2. Description of the Related Art
As an image forming apparatus, an inkjet printer (inkjet recording apparatus) is known, which comprises an inkjet head (liquid ejection head) having an arrangement of a plurality of nozzles (ejection ports) for ejecting ink (liquid). The inkjet printer can form an image on a recording medium by ejecting ink from the nozzles toward the recording medium while the inkjet head and the recording medium are caused to be relatively moved to each other.
For example, as an ink ejection method used in such an inkjet recording apparatus, a piezoelectric method is known, in which a diaphragm which forms one face of a pressure chamber (ink chamber) is deformed by deforming a piezoelectric element, and thereby the volume of the pressure chamber is changed. Ink is introduced into the pressure chamber through an ink supply passage when the volume of the pressure chamber is increased, and the ink inside the pressure chamber is ejected from the nozzle in the form of an ink droplet when the volume of the pressure chamber is decreased.
Furthermore, in recent years, it has been sought to form high-quality images similar to photographic prints, with such inkjet recording apparatuses. For this purpose, it is required to reduce the size of the ink droplets ejected from the nozzles by reducing the size of the nozzles much further, and to arrange the nozzles at higher density.
This requires the pressure chambers which are connected to the nozzles to be disposed in a high-density arrangement, in conjunction with the increased density of the nozzles. Furthermore, the electrical wires which supply drive signals to the piezoelectric elements disposed corresponding to the pressure chambers, are also required to be arranged at higher density.
In order to achieve higher density arrangement of the nozzles in this manner, various proposals have been made.
For example, Japanese Patent Application Publication No. 9-314833 discloses an inkjet print head. It is an object of such an inkjet print head to avoid operational errors in the driving of the inkjet print head having high nozzle density, and to reduce the costs of manufacturing the head. In the inkjet print head, pressure chambers are arranged in a horizontal direction with respect to the print surface; piezoelectric elements are arranged on a diaphragm that forms the upper surface of the pressure chambers; a reservoir (common liquid chamber) for supplying ink to the pressure chambers is arranged above the diaphragm; and wires from the piezoelectric elements are extended horizontally and connected to TFTs (thin film transistors) arranged on a drive circuit board located perpendicularly to the piezoelectric elements, instead of using a costly high-density FPC (flexible printed circuit).
Furthermore, for example, Japanese Patent Application Publication No. 2003-127366 also discloses an inkjet print head. It is an object of such an inkjet print head to maintain the good ink ejection performance, and to reduce the head size. In the inkjet print head, pressure chambers connected to nozzle apertures are formed in a flow channel forming substrate; and a reservoir forming substrate (piezoelectric element cover) is bonded to the same side of the flow channel forming substrate as the piezoelectric elements. The reservoir forming substrate seals off a free space in the region which opposes the piezoelectric elements and does not block the movement of the piezoelectric element. An electrical wire is provided on the inner surface of the reservoir forming substrate, and by bonding it with the flow channel forming substrate, the wire is electrically connected with the common electrode of the piezoelectric elements.
However, in such a head described in Japanese Patent Application Publication No. 9-314833, since the wires from the piezoelectric elements are extended horizontally and connected to the TFTs, wiring of high-density for the arrangement of the piezoelectric elements corresponding to 1000 dpi (dots per inch) or more is difficult to be achieved. Furthermore, in such a head described in Japanese Patent Application Publication No. 2003-127366, the electrical wires are provided on the inner surface of the reservoir forming substrate (piezoelectric element cover). Accordingly, though the head is prevented from becoming large in size, it is difficult to achieve high-density wiring.
For example, in a full line head which covers the whole width of the recording medium, if the piezoelectric elements are arranged in a matrix configuration in order to achieve a high-density arrangement of 2400 dpi, then it is required to extend each wire from each of the piezoelectric elements. In this case, the line intervals between the wires are 10 μm or less, and it is difficult to achieve such high-density on the basis of a method where the wires are formed by etching or plating.